The invention relates to a road test simulator and to a method for synchronizing control of a road test simulator.
In order to inspect a vehicle after its final assembly, various tests are ordinarily conducted. These tests are often carried out as actual road tests, which renders the testing costly.
So as to abbreviate or to completely replace such costly road tests, it is known in the art to provide a road test simulator, which can be used to simulate the irregularities of a road surface. Most prior-art simulators, however, have rollers with a non-adjustable profile. As a result they are inflexible and thus suitable only for limited testing of a vehicle.
German reference DE 299 18 490.0 describes a road test simulator with profiled rollers. Each of these rollers is provided with a plurality of profile-imparting blocks along its outer circumference. These blocks can be adjusted in the radial direction of the roller to change the profile of the roller. Each roller ranges in width from a single to a double width of the vehicle tire. The road test simulator is additionally provided with a computer unit to implement a test program. With the aid of this test program, the computer unit can be programmed, for example, to simulate different road surfaces automatically by adjusting the blocks of the rollers.
Also, U.S. Pat. No. 4,635,472 discloses an apparatus for testing a vehicle. Each vehicle of the vehicle to be tested has a corresponding own rotary drum. Every rotary drum is driven by a separate synchronous electric motor. The motors are coupled via a common frequency control unit to an electric power source. To ensure that the synchronous motors have the same rotational speed, changes in torque are detected by torque measurement devices respectively coupled to each motor. The measured values of the torque measurement devices are supplied to a central evaluation device, which derives an adjustment signal for the central frequency control unit.
European Patent Application 0 567 781 discloses a method and an apparatus for controlling electric motors. Two or more motors with defined differences in rotational speed are to be driven. This is accomplished using sensors to generate pulse trains in response to increasing swing angles of the motors. The motors are then temporarily either partly or completely disconnected from the power supply on the basis of the differences in the pulse trains.
In addition, it is conventional in the art to ensure that the rollers of a road test simulator are synchronized, through the use of a mechanical coupling of the rollers.